Meeting Abstract
P2-9 - Differences in diel patterns of cortisol but not glucose in wild redband trout in perennial versus intermittent streams Jirik, AM*; Wooding, AP; Pradhan, DS; Idaho State University; Idaho State University; Idaho State University annajirik@isu.edu
Maintenance of homeostasis due to chronically high thermal stress increases energetic costs in vertebrates. The gluconeogenic hormone, cortisol, circulates at higher levels to provide organisms with the required energy to survive their stressful circumstance. Redband trout (Oncorhynchus mykiss gairdneri) are a cold-water species that have adapted to survive in warm, arid, desert streams, under environmental conditions that are outside of the optimal temperature ranges of many other salmonids. Here, we measured plasma cortisol and glucose among redband trout (N=480, >2y) from two cold montane and three hot desert sites in South West Idaho from June through October. We hypothesized a positive correlation between cortisol and glucose levels, because higher glucose levels are known to compensate for the increased energetic demand during stressful periods. However, there was no relationship in cortisol and glucose in fish from either montane or desert environments. Thus, glucose energetics might be affected by other factors. Across fish from all streams, there was also a somewhat strong, significantly non-zero positive relationship between water temperature and average cortisol concentrations (R2=0.74, p < 0.0001). We also analyzed diel patterns in cortisol levels for fish from each stream. Among the four perennial streams, there was a negative relationship between the time of day at collection and cortisol concentration, three of which were significant. Fish from the intermittent stream, however, had a significant positive relationship between the two variables. This may be due to increased thermal fluctuations that accompany reduced stream depths. This suggests that temperature does have an effect on stress levels in redband trout, however there seems to be many more phenomena that influence stress levels, especially in natural settings.